The hard and tough properties of ceramic materials would make them a useful material for machined parts in many areas. However, the high cost of machining ceramic materials has prevented their extensive use for parts requiring machining, such as, precision parts, engine parts and bearings. Current technology relies on forming a shape as close as possible to the desired part and then repeatedly grinding and polishing the shape until the desired part is obtained. This method is not of great utility. It is desirable in the industry to have a process for the bulk removal of ceramic material from the formed shapes, i.e., machining, so that parts can be produced from raw stocks of simple shapes, like rods and flats. However, the hardness and brittleness of ceramics has made machining of these materials difficult and costly. Currently, in general, very hard surfaced tools, such as, diamond tools, are required to machine the ceramic materials. These tools are expensive and their rate of consumption is rapid. Increasing the machining force can increase the material removal rate but it is detrimental to the part being machined since the higher force will induce a high rate of fracture and failure in the part. Accordingly, the current practice is to repeatedly remove small amounts of the material to avoid forces which may form residual surface cracks and failures in the ceramic part which renders it unusable.
In addition to this conventional process for machining ceramic materials, other processes have found limited use for special applications. These processes include machining by: ultrasonics, abrasive jet or water jet, ductile grinding, ultra-stiff machinery, electro-chemical means to dress the wheel, and lasers. However, only the conventional method using diamond tools has found any commercial significance. A further background discussion is provided in, D. P. Stinton, "Assessment of the State of the Art Machining and Surface Preparation of Ceramics" ORNL Report to DOE ECUT program DE-AC05-84OR21400 (November 1988).
Yasunaga et al., "Mechanism and Application of the Mechanochemical Polishing Method Using Soft Powders", NBS Sp. Pub. 562 (1979), disclose the use of barium carbonate powders for the improved polishing of silicon ceramics. Improved polishing of quartz by Fe.sub.3 O.sub.4 and MgO has also been disclosed. Also, Vora et al. disclose the use of Fe.sub.2 O.sub.3 and Fe.sub.3 O.sub.4 for polishing silicon nitride, "Mechanochemical Polishing of Silicon Nitride", Am. Cer. Soc., P.C140 (September 1982), and the polishing of boron carbide by NiO or SiO.sub.2, "A Study of Mechano-Chemical Machining of Ceramics and the Effect on Thin Film Behavior", Off. of Naval Res., No. N00014-80-C-0437-2 (1983). The polishing of silicon carbide with SrCO.sub.3 is also known. All of these teachings suggest the easy removal of a thin film, usually less than 100 Angstroms thick, without directly abrading the surface upon which it is formed. These processes result in a reduction in surface damage but in no significant increase in the machining rate. None of the processes provided an improved machining rate over the conventional diamond tool cutting methods.
It is further known in the art that compositions containing halogenated hydrocarbons are useful as cutting fluids or polishing fluids for the machining or polishing of metals. U.S. Pat. No. 999,941, U.S. Pat. No. 3,282,665, and U.S. Pat. No. 3,618,461.
Finally, it is also known from U.S. Pat. No. 4,731,349, that ceramics, such as alumina, may be ball milled in a suspension of a liquid, such as carbon tetrachloride, which is taught to be inert to the ceramic.